Social interactions are the touchstone of human sociality. They serve two key roles: (1) to help people learn from others? experiences without needing their own firsthand experience and (2) to engender social bonds between individuals. How do speakers and listeners bridge epistemological gaps in order to transmit knowledge? How does communication give rise to social connection? The proposed project will adopt novel neuroimaging methods to peer into the minds of communicators as they verbally exchange thoughts with one another. This approach enables us to identify the cognitive and neural processes by which social interactions produce successful information transmission (i.e., sending and receiving of information) and perceived social connection (i.e., interpersonal closeness). We start by exploring the component parts of communication ? sending and receiving information ? as well as the outcomes of each. In Aim 1, we examine how successfully sending and receiving instructional con- tent evoke neural alignment between senders and listeners. We then explore the ways in which the whole of human communication is greater than the sum of these component parts. Real interactions are dynamic: peo- ple rapidly formulate ideas into words, translate each other?s words into ideas, and respond in rapid-fire turn- taking. Most research into social interaction has relied primarily on paradigms that do not allow for real social interaction: participants often engage in one-sided interactions, passively view stimuli in parallel, or interact through contrived scenarios. Previous work that has studied real social interactions most often does so us- ing more static behavioral measures or neural measures with lower spatial resolution. Our unique research site, with two MRI scanners in adjacent rooms, allows us to do both simultaneously. The current proposal thus offers a shift from conventional paradigms to naturalistic ones, in which real dyads converse in real time. In Aim 2, we examine how neural alignment during social communication differs across dyads with strong and weak levels of social connection. We design the communication task such that speakers and listeners must actively anticipate each other's words and plan their own words accordingly. Novel inter-subject correlation measures will focus on identifying the role of synchrony and prediction in communication. We will measure these neural dynamics in speakers and listeners with a range of success in transmitting information (e.g., individual differences in properly providing and following instructions) as well as dyads with strong and weak social connection (e.g., friends vs. strangers; roommates at the start and end of the year). These studies, by focusing on temporal dynamics within a dynamic and naturalistic social interaction, allow us to identify the cognitive and neural processes by which communication gives rise to learning and so- cial connection.